let _Vue = null

class VueRouter {
  static install(Vue) {
    //1.判断当前插件是否已经安装
    //3.把创建Vue实例传入的router对象注入到实例上
    if (VueRouter.install.installed) {
      return
    }
    VueRouter.install.installed = true
    //2.把vue构造函数记录到全局变量
    _Vue = Vue
    //3 把创建Vue的实例传入的router对象注入到Vue实例
    // _Vue.prototype.$router = this.$options.router
    _Vue.mixin({
      beforeCreate() {
        if (this.$options.router) {
          _Vue.prototype.$router = this.$options.router
        }
      }
    })
  }
  constructor(options) {
    this.options = options
    this.routeMap = {}
    this.data = _Vue.observable({
      current = '/'
    })
    this.init()
  }
  init() {
    this.createRouteMap()
    this.initComponents(_Vue)
    this.initEvent()
  }
  createRouteMap() {
    //遍历所有的路由规则，把路由规则解析成键值对的形式，存储到routemap中
    this.options.routes.forEach(route => {
      this.routeMap[route.path] = route.component
    })
  }
  initComponents(Vue) {
    Vue.component('router-link', {
      props: {
        to: String
      },
      render(h) {
        return h(
          'a', {
            arrts: {
              href: this.to
            },
            on: {
              click: this.clickhander
            }
          }, [this.$slots.default]
        )
      },
      methods: {
        clickhander(e) {
          if (this.options.mode === 'history') {
            History.pushState({}, '', this.to)
            this.$router.data.current = this.to
          } else {
            window.location.href = window.location.origin + this.to
            this.$router.data.current = this.to
          }

          e.preventDefault();
        }
      },
    })
    const self = this
    Vue.component('router-view', {
      render(h) {
        const cm = self.routeMap[self.data.current]
        return h(cm)
      },
    })
  }
  initEvent() {
    if (this.options.mode === 'history') {
      window.addEventListener('popstate', () => {
        this.data.current = window.location.pathname
      })
    } else {
      window.addEventListener('hashchange', () => {
        this.data.current = window.location.hash.slice(1) || '/'
      })
    }


  }

}